Einishing of liquid polymers



Patented Julyll, 1950 J assign'ors to standardoil Devlopment Company, a corporation of pelaware No Drawin This invention pertains to the preparation of liquid. products bythe polmerization of conjugateddioleii'ns or 'rn iritur'es' containing conju ated dioleffins in aqueous emulsion and particularly .a i l d art n su aproducts.

As described in U. s. Serial No. 637,782 filed Patem er a 45 y 'P- Fren h B- M- derbilt', and M. W? S yyaney, 'n'oyv Patent No 2,500,983, it has been found that liquid polymers can be prepared by theemulsion polymerization of conjugated diolefins suchas'butadien, isoprene, piperylene, dimethyl butadiene, 'inethyl pentadiene, or' the like; and from mixtures of "a major proportion o f'such'conjugated diolefins and a minor proportion of an unsaturated comonomer such as styrene, alpha methyl styrene, alpha methyl para methyl styrene, halogenated styrenes such as chlorinated and brioininate'd styrenes, acrylonitrile, methacrylonitrile, acrylic and methacrylic acid esters such as methyl acrylate. and methyl imethacrylate, fumaric acid esters such asethyl furnarate and unsaturated ketones such as methyl vinyl ketone and methyl isopropenyl ketone, ;by proper control of the reaction conditions. Specifically it was found that i u d po ymers wer obta ned by us n a ve y igh conc nt io s (1,- at lea t 3 i per c nt based on th mo om vo a aliphatic mercaptan polymerization modifier Applicationcfictpbn serial 932 .9

t glailns. (c1. zen-s and/o u in a hi ly unsaturat at a id 9 prebarieg t e 89 a li ls a ebe p me pta .p m t l t m fi mb ned chain length of at least 5" carbon atoms maybe used, est mony; of modifier yarying .betwe 3% and 109 2 Wat-[ex m the m a"v 1 time 3 t P-equa d me cabtan ela yad a d t art cu ar t ieea ml meri' Q1 souglit. Ter ia y ne captae a 'reierred t ti prima y or ary mer ap a l s but "a th t pe may be: 'ntae us y mplQ ad- Fo a mi a that; Bear? 9; the te tiar me a t derived from the "dimer ofgisobutylene, or abeut 519% net na is o eriy e qm t e Prime 1 1 251. a 9 e ti .aeet

case

containing 16 carbon i e s and'fthese s am ed aey be 122 the ter ia ty e" II! Ineans oi tanfalkaline learthinetal salt or their part of the modifier maybe added initially and the remainder may be added portionwise durmg the reaction. PortionWise addition or the modifier is'especiall-y desirable when the polymeg-anion reaction" is carried substantially to completion or 100% monomer conversion.

Fatty acids which maybe used in the preparation of soap emulsifiers are preferably those derived from drying oils such as linseed oil or soybean oil although other acids such as oleic, myristic, stear-ic or abietic acids may also -be"u'sed' By using soaps of highly unsaturated fatty acids as emulsifiers, it is possible toreduce the amount of 'mercaptan or other polymerization'modifier'. lhe amount of emulsifier isiabout 0.25 to about 5 uit'per cent and the amount of polymerization catalyst is about 0.1 to about 1 wt. per cent'based upon the monomers The readtion is carried out atitergri per'aftures abova about 130, k C. and preferably at temper'atursthat somewhathig'her than are used in the produ not solid rubbery polymers by emu sion polyme .lzatiorll The 1 01 ime'r' is e oy e b breakin the esultant "latex with? sodiumfch' oride b ine, bymea b he and an acid such as acetic "or sulfuric acids," by

salt which c9ll ertsthe soap "into a ater- 91? f rm h he mi s it imam th qi ypql iae ar th a X means of a yatersolu'ble'o s ioi qtyl 901 9 teet 1 c V s were vera im with a a l ith alkali and then dried; The'resi iltantproducts are liquid polymerico'ils, free iro'inrubbifylflrod ucts, eyen when the reaction' is carried'td f-j90% monomer conversion a d" sa'i'd oilshalifeandfltlr'i'n'si c'yiscosity'Qibet 'eenQDS angina." The any li id. pblyldlltadlene ordinarily "have an intrinsic viscosity of between 0.1 and 0.2 while the oily liquid copolymers of butadiene and styrene prepared by this technique have an intrinsic It is also the object of this invention to prepare polymer oils of such color, clarity and drying properties as to be suitable for use as a drying oil.

These and other objects will appear more clearly from the detailed description and claims which follow.

We have now found that polymer oils of improved clarity, color and drying properties are obtained by creaming the polymer latex with ization are obtained by adding 3' parts of mercaptan initially, one part at 35% and another part at 55% conversion.

The polymerization is ordinarily carried to not more than about 70% conversion, since above this point the intrinsic viscosity of the polymer increases rapidly unless incremental addition of the mercaptan is resorted to. This conversion can ordinarily be obtained in from 8 to 10 hours at temperatures of 40-45 C. depending upon the amount of activator used..

It is ordinarily preferred to add a suitable antioxidant such as hydroxylamine or hydroxylamine hydrochloride ditertiary butyl cresol and the like in order to prevent further polymerization. Unreacted monomers may be removed from the product by the usual methods employed in the stripping of synthetic rubber latices as by flashing off at atmospheric or sub-atmospheric pressure with or without the help of an inert stripping agent such as steam, nitrogen or the like. If desired,

' unreacted mercaptan can be removed from the brine, coagulating with an alcohol such as isopropyl alcohol or gaseous or solid CO2 or a combination of alcohol and CO2, reslurrying the coagulate several times with water and two or three times with dilute alkali, finally reslurrying with alcohol, separating the coagulate from the alcohol, dissolving the coagulate in a low boiling solvent which has a substantial solvent power for the polymer oil but substantially no solvent power for soap and gelled or cross-linked polymer, filtering the resultant solution and subjecting the filtrate to vacuum drying to remove the solvent and any residue of alcohol or water that may remain in the polymer oil. The oils obtained in this way possess good color due to the low temperature used for the only polymer drying step, and the resultant oils are very clear due to substantially complete absence of soap residues and also gelled or cross-linked polymer. The polymer oils thus treated have the further advantage that they air dry readily.

The polymers are ordinarily prepared from the following recipe:

1 Parts Butadiene (or hydrocarbon monomer mixture 100 Soap 3 Potassium persulfate 0.3 Potassium ferricyanide 0.15 Diisobutylene mercaptan 5.0

Water 180 In the preparation of diolefin-nitrile copolymers, morpholine is used as the activator instead of potassium ferricyanide.

The amount of soap used as emulsifier is preferably the smallest amount that will give a stable emulsion. It is also preferred both from the standpoint of product quality and convenience of carrying out the reaction to effect a secondary activation in addition to the persulfate, i. e., by the addition of potassium ferricyanide in the case of hydrocarbon polymers such as polybutadiene or butadiene-styrene copolymers or with morpholine in the case of butadiene-acrylonitrile copolymers. Tertiary octyl mercaptan (diisobutylene mercaptan) is the most satisfactory polymerization modifier since lower molecular weight mercaptans show little promotion of the polymerization while higher molecular weight mercaptans than Cs show better promotion, but inferior modifying properties. form molecular weights throughout the polymer- Polymers of uniproduct by subjecting it to steam stripping at reduced pressures.

. The latices may be coagulated by the addition thereto of about 0.? part of brine (by volume) for each part (by volume) of latex, preferably together with sufficient carbon dioxide to adjust the coagulate particle size so that coalescence of fine particles occurs. In order to avoid redispersion of the coagulate during the first water slurry, it is necessary to add at least one part of isopropyl alcohol to each 20 parts of latex during coagulation. The final coagulate is in the form of a semi-fluid mass and the aqueous liquor is drained from this coagulate.

To further insure against redispersion of the low molecular weight polymers, it has been found advisable to use a 5.0% solution of isopropyl alcohol in water for the first slurry wash. The coagulate is reslurried several times with water and at least once and preferably two or three times with dilute alkali to remove soap and brine followed by at least one water wash. The coagulate is finally reslurried with isopropyl alcohol to remove any residual unreacted mercaptan whereupon as much of the alcohol as possible is removed from the coagulate by decantation. Instead of reslurry washings as described, the washing may be effected by dissolving the polymer oil in a water-insoluble solvent and applying countercurrent water and alkali washings.

In order to purify the polymer and render it substantially free of soap and gelled polymer, and to improve their drying properties, the coagulate is dissolved in from an equal volume to several volumes of a suitable solvent. Hydrocarbonsoluble coagulates are dissolved in pentane or a .catalytically cracked C5 cut boiling within the range of -102 R, which is free from heavy ends. If it is desired to avoid freezing of the filter bed in vacuum filtering of the solution or evaporation losses encountered with such highly volatile solvents, it is possible to utilize a higher boiling out such as a process naphtha of ZOO-240 F. boiling range. This solvent also should be free from high boiling or heavy ends. Higher boiling solvents are not desirable inasmuch as the temperatures necessary to remove them from the polymer oils, is so high that the oil becomes badly discolored. Since drying temperature must be sufficiently high to drive off water, the solvent used may have a boiling point up to about 240-250 F. without causing undue discoloration. In the case of by continuous processes;

air or baked to dryness.

'aewese drocarbon insoluble polymers jsuch as dioleiiinnitrile copolymers and the like, the solventkmay beaceto'n'e, met'h-ylf-etheyl ketone, or other low Flo Super Gel (Johns Man-ville) claw Solutions of -30% polymer oil in pentane or other low boiling solvent can be clarified by asingle pass through about a one-half-"ihchbed of this filter aid. Otherfilter aids which may be used include .Attapu'lgus clay, bentonlte clay; Super Filtrol;

(diatomaceous earths) asbestos, animal charcoal; etc. Either: ressure, vacuum or gravitation methods of filtration may-be employed. Instead of filtering the polymer oil-solutions in'order to effect clarification thereof, theymay also be centrifuged to give clear oils in either batch or The addition or small amounts of such materials "-I-Iy-Flo to the solutions prior-tocentriiuging seems to-have certain advantages but is not essential.

, The filtrate or the clarified solution obtained on centrifuging is then subjectedto avacuum drying operation. Solvent i'sflashed off; vacuum and heat applied to thepolymen solutions. The

polymer oil was-heated toabout 160-180 I. and

vacuum of about 22 to. 26 incheso'r mercury were applied, to give system pressures well below the vapor pressureof Water -at the operatingtemperatures.

and/or the vacuum maybe increaseditoagivesystem pressures below the vapor pressure of the highest boiling solvent: at. the operatingctemperature. r

The resultant polymer oils are .oiexcellent color and clarity and. may b.e..read-ily-dried in air- They may, accordingly, be used as drying oils in paints and other coating compositions Materials such as cloth, leather and paper may be rendered resistant to the effects ot agent's such as water, organic solvents and grease-by surface coating or impregnating these materials with these polymeric oils. Following impregna tion or coating; the articles are'eithr dried in In either case driers such as are in common use as accelerators for drying oils can be used to shorten the drying times. The final articles are not discolored and retain all of their originalflexibility. Since these polybutad iene polymer oils possess unsaturation of the type and in the amounts'found in rubber,

they may be vulcanized by methods in common use for polymers of high unsaturation' to give flexible and resistant coatings;

The following examples are illustrative of. the

present invention.

' V Exempted At m'onomer conversions of. approximatelyazfi and:150%,---an additional: onmercaptam-was With high-er boiling solvents'suchas that of 200-240" F. boiling range, the temperature added meking a total of-aoparts on the butadiene.

After 7.0-hours reactiontime at 45 0., of the monomer had been converted to polymer andthe reaction mixture was dumped, the latexshort-stopped with 0.1% hydroxylamine, and unreact'ed butadiene stripped from the latex.

The homogeneity or the polymer produced illlstraited .b'ythej. following intrinsic viscosity do, a; I

I Per Cent conversion Int. Vie.

The stabilized latex was coagulated with 0.7 volume of brine, and, 0.05 volume of isopropyl alcohol per volume. of latex. This coagulate was washed four times. by slurrying' warm distilled water. Thelcoag'ulate was then given a final alcohol wash and dried by heating at atmospgieric pressure at temperatures not exceeding 1 C'..

The final polymer was very cloudy in appearance. A sampleof. this product was dissolved in n-pentaneto give a solution of." about 30% concentration. The solution was filtered through abed of. 'Hy-Flo filter aid. and the pentane then was stripped from the flltrate by heatingunder vacuum. The residue filteredirom the solution was recovered and dried;

Analyses andobservationsconcerning the original polymer and; the two fractions obtained therefromare listed below:

These data show that theypurification procedure employed has not only" clarified the oil but has also purified it of soapcontaminants'.

Example 2 A liquid polymerof butadiene' was prepared in accordance with the recipe given in Example ,1; A conversionof 725% was obtained after 7 hours polymerization at"4"5' C; The latex was short-stopped with 0.1% hydroxylamine and coagulated with brine and alcohol. This coagulate" was washed once withwater' to remove any traces or brine. occluded. in the coagulate. The coagulate was" then divided into two parts (A) and C); Partj A was dried at C. togi've a can; colored viscous polymer. Part of this material'ihereafter referredlto as Part (18)) was dissolved ini pentane, fill'teredl through Hy-F lo filter aid and thendriedlunder vacuum- The polymer whichwasisomted was clear butdark colored. p

Part C (original coagulate) was dissol'vedin pentane" andfiltered through Hy-Flo filter aid. A layer Of water was removed" from the" nitrate and the remaining p'entanesolution'" was then .lreated -und'err wacuumt until: the: solventhad 7 been completely removed; 1- They .final polymer in this case was clear and light colored. Data obtained on these .three oils are summarized below:

These data again illustrate the advantages in oil appearance and purity gained by use of pentane solutions and filtrations.

' Example 3 A polybutadiene oil was prepared in accordance with the recipe given in Example 1 in pilot plant equipment using a 110# butadiene charge. A conversion oi 69% was obtained after 8 hours polymerization at 113 F. and the run was terminated at this conversion. The latex was shortstopped with 0.1% hydroxylamine and then coagulated with brine and-carbon dioxide. The coagulate was washed with water and caustic solutions by reslurr'ying in an open vat.

A sample of the washed polymer was withdrawn atthis point and split into two parts (A and B). Part A was dried by heating at 125 C. while Part B was dissolved in pentane, filtered and then dried in a-manner already described. The following data indicate the advantages of dissolution and'filtration.

Polymer. Appearance ar Part A 0.107 Cloudy-dark colored 1. 73 Part B 0.105 Clear-Light colored. 0. 04

Example 4 An oily copolymer of butadiene and acrylonitrile was prepared by using the charge Parts The polymerization was carried out at 35 C. and required 10 hours to reach a conversion of 70%. One-half of the mercaptan was added to the charge initially and A was added at 25 and at 50 conversion. a

The latex was short-stopped with- 0.1% bydroxylamine and coagulated with brine and alcohol. The coagulate was washed once with 0.25% sodium hydroxide solution, and three times with water. The washed coagulate was then dried at temperatures not exceeding 140 C. This polymer was quite cloudy but when it was. dissolved in acetone and filtered through a bed of I-Iy-Flo, a clear filtrate was obtained. This filtrate yielded a clear, fluid polymer. Analysis of this polymer gave the following results:

Intrinsic viscosity 0.12 Percent nitrogen 6.66 Percent soap 0.12 Percent fatty acid 0.23

. Ihe foregoing description contains a limited 8 numberof embodiments of the present invention. It willbe understood, however, that the inven-' tion is not limited to the specific conditions dis-' closed since numerous variations are possible withoutdeparting from the scope of the following claims.

What we claim and desire to secure by Letters Patent is; 1 v

1. In the process of purifying polymeric drying oil obtained by polymerizing butadiene-1,3 in aqueous emulsion in the presence of 0.25 to 5.0 weight percent based on monomers of a sodium soap ofa fatty acid and in the presence of 3 to 8 weight per cent based on the monomers of an aliphatic mercaptan of from 8 to 16 carbon atoms, coagulating the resultant emulsion of polymer in reaction medium, separating the polymer oil coagulum, -and washing the coagulum with water, alkali and alcohol,. the steps of dissolving the polymer oil coagulum in normal pentane, filtering the resultant solution through'a clay filter aid and evaporating the solvent from the filtrate.

2. In the process of purifying a polymeric drying oil obtained by polymerizing a conjugated diolefin of 4 to 6 carbon atoms in aqueous emulsion in-the presence of 3 to 12 weight percent based on monomers'of an aliphatic mercaptan having 5' to 16 carbon atoms and 0.25 to 5.0 weight percent based on monomers of an emulsifier, coagulating theresulting emulsion of oily polymer, separating the coagulated oily polymer and washing the separated polymer with water, the improvement which comprises dissolving the oily polymer in a hydrocarbon solvent having a boiling range between and 250 F., and filtering the resulting solution.

3. In the process of purifying a polymeric drying oil having an intrinsic viscosity between 0.05 and 0.4 and obtained by polymerizing butadiene- 1,3 in aqueous'emulsioninthe presence of 0.25 to 5.0 weight. percent based on monomers of a fattyacid soap emulsifier and 3 to 8 weight percent basedon'm'onomers of a tertiary aliphatic mercaptan having from 8 to 16 carbon atoms, 00- agulating the resulting aqueous emulsion of oily polymer, separating the oily polymer from the coagulated emulsion and washing the separated polymer with water, alkali, and alcohol, the improvement which comprises dissolving the washed oily polymer in a hydrocarbon solvent having a boiling range. between 90 and F., filtering theresulting solution to separate soap and insoluble gel polymer-therefrom and evaporating the solvent from'the filtrate.

4. In theprocess of purifying a polymeric drying oil having an intrinsic viscosity between 0.1 and 0.4 and obtainedby polymerizing butadiene- 1,3 in aqueous emulsion in. the presence of 0.25 to 5.0 weight percent. based on monomers of an emulsifier consisting of a sodium salt of tallow acid and in the presence of 3 to 8 weight percent based on monomers of diisobutylene mercaptan, adding brine and isopropyl alcohol to the resulting aqueous emulsion of oily polymer and thereby breaking the-emulsion, separating the oily polymer from the aqueous portion of the broken emulsion and washing the separated oily polymer with-water, alkali, and isopropyl alcohol, the improvement which'co'mprises' dissolving the oily polymer in such an amount of normal pentane that a solution containing 25 to 30% of polymers is formed, filtering the resulting solution through a bed of clay filter aid' an'devaporating the pentane at a temperature-between and F.

undera vacuum of 22 to;26-i.nches of mercury.

5. A process according to claim 4' wherein the polymeric drying oil is obtained by copolymerizing a, major proportion ofbutadiene-IB and a I minor proportion of styrene.

6. A process according to claim 4 wherein the polymeric drying oil is obtained by copolymeriz- REFERENCES CITED The following references are of record in the file of this patent: I

10 UNITED STATES PATENTS Number Name Date 1,254,866 Thiele Jan. 29, 1918 2,067,854 Macdonald Jan. 12, 1937 2,099,513 De Simo Nov. 16, 1937 2,142,592 Waligora Jan. 3, 1939 2,252,333 Rothrock Aug. 12, 1941 2,255,729 Britton Sept. 9, 1941 FOREIGN PATENTS Number Country Date Great Britain 1912 OTHER REFERENCES Snyder et a1.: Jour. Am. Chem. Soc., vol. 68, 1422-1431 (1946). 

2. IN THE PROCESS OF PURIFYING A POLYMERIC DRYING OIL OBTAINED BY POLYMERIZING A CONJUGATED DIOLEFIN OF 4 TO 6 CARBON TOMS IN AQUEOUS EMULSION IN THE PRESENCE OF 3 TO 12 WEIGHT PERCENT BASED ON MONOMERS OF AN ALIPHATIC MERCAPTAN HAVING 5 TO 16 CARBON ATOMS AND 0.25 TO 5.0 WEIGHT PERCENT BASED ON MONOMERS OF AN EMULSIFIER, COAGULATING THE RESULTING EMULSION OF OILY POLYMER, SEPARATING THE COAGULATED OILY POLYMER AND WASHING THE SEPARATED POLYMER WITH WATER, THE IMPROVEMENT WHICH COMPRISES DISSOLVING THE OILY POLYMER IN A HYDROCARBON SOLVENT HAVING A BOILING RANGE BETWEEN 90 AND 250*F., AND FILTERING THE RESULTING SOLUTION. 